tbuckley/cabot-search huggingface dataset:
Abstract P3149: Effect Of SGLT2 Inhibitors On Atrial Fibrillation Susceptibility In Diabetic Mice
Authors: Jonathan Granger, Pauline Nguyen, Olurotimi O Mesubi
Journal: Circulation Research (2023)

Background: Diabetes mellitus (DM) and heart failure (HF) are independent risk factors for atrial fibrillation (AF), the commonest clinical arrhythmia. A new class of drugs - sodium glucose cotransporter 2 inhibitors (SGLT2i) have beneficial effect in DM and HF and are now part of the guideline directed therapy for HF. However, conflicting evidence exists regarding their role and effect on cardiac arrhythmias including AF independent of their effect on HF and their exact mechanism(s) of action on the heart. Objective: Here we tested the effect of two commonly used SGLT2i on AF susceptibility in a type 2 DM (T2D) mouse model. Methods and Results: We used a T2D mouse model (high fat diet + low dose streptozocin) and a cohort of T2D mice were treated with SGLT2i - Empagliflozin (30mg/kg/d) or Dapagliflozin (5mg/kg/d) for 10 weeks in drinking water. We performed invasive electrophysiologic studies (EPS) to assess AF susceptibility by a rapid atrial burst pacing protocol in male mice aged 5 months at the time of EPS. T2D mice had increased AF susceptibility compared with non-diabetic littermate controls (normal chow diet + citrate buffer) [78% (14/18) vs. 28% (5/18), p &lt; 0.01]. T2D mice treated with Empagliflozin were protected from increased AF susceptibility (22% (3/18) [p &lt; 0.01]) while T2D mice treated with Dapagliflozin were not protected from increased AF susceptibility (58% (11/19) [p = 0.29]). Both Empagliflozin and Dapagliflozin treated T2D mice had normalization of their blood glucose levels to comparable levels with the non-diabetic control mice. T2D mice had mild LV dysfunction compared with non-diabetic controls (EF - 66% vs 81%, p &lt; 0.01) and treatment with either Empagliflozin or Dapagliflozin attenuated the degree of LV dysfunction (EF - 71% in both groups). Conclusion: Taken together, our data support the concept that SGLT2i decrease AF susceptibility in hyperglycemia primed AF, in addition to attenuating LV dysfunction in T2D. However, the effect on AF was only observed with Empagliflozin but not Dapagliflozin treatment independent of their effect on hyperglycemia and LV dysfunction. Further investigations are necessary to determine if there is a class effect of SGLT2i on AF susceptibility and the specific mechanisms of action modulating this effect.
Abstract P1147: Cardinal Is A Nuclear Lncrna That Represses SRF/TCF-mediated Gene Transcription By Co-occupying SRF/TCF-bound Gene Promoters In The Heart
Authors: Jessica Perciaccante, Fnu Priyanka, Pornthida Poosala, Xiaorong Parks, Tamlyn Thomas, Douglas M Anderson
Journal: Circulation Research (2023)

LncRNAs are an emerging class of co-transcriptional regulators important for balancing gene expression networks in the heart during development and disease. We recently characterized a cardiac-specific lncRNA named CARDINAL, which is transcribed adjacent to the SRF-coactivator myocardin. Myocardin, and members of the ternary complex factor (TCF) family (Elk1-4), compete for interaction with SRF to balance opposing transcriptional networks in the heart. Previously we showed that CARDINAL forms a stable complex with SRF and can repress SRF/TCF-mediated gene transcription, suggesting CARDINAL functions as an RNA cofactor for SRF. Here we show using RNAscope in situ hybridization that CARDINAL is a nuclear lncRNA in both mouse and human cardiomyocytes. To identify CARDINAL-regulated genes, we performed Chromatin Isolation by RNA Purification (ChIRP) using anti-sense oligonucleotides specific to endogenous CARDINAL in HL-1 cardiomyocytes, followed by deep sequencing. CARDINAL transcripts were localized at ~100 genes, with the majority (76%) of CARDINAL peaks occupying the transcriptional start site (TSS) of gene promoters. Strikingly, the majority of CARDINAL ChIRP peaks overlapped with SRF-bound ChIP peaks in the cardiac genome. Homer motif analyses of CARDINAL peaks identified enrichment for the SRF CArG box and TCF binding motifs for Elk1 and Elk4. Consistent with our previous findings, CARDINAL peaks were localized to canonical SRF/TCF-regulated genes, including Egr1, Elk4, and components of the AP-1 complex, such as c-Fos, Junb, and Jund. These findings highlight CARDINAL, similar to its protein coding neighbor gene myocardin, as a co-regulator of SRF-dependent gene transcription. CARDINAL, however, in contrast to myocardin, can repress SRF/TCF-dependent gene transcription, which is likely mediated by its unique ability to co-occupy SRF/TCF-bound gene promoters.
Abstract P2128: Insight Into Glycogen Synthase Kinase 3 Beta Localization Within The Heart: Role On Ischemia Reperfusion Injury
Authors: Marilen Federico, Stephen Hurst, Hui-Ying Tsai, Facundo Barraque, Shey-Shing Sheu
Journal: Circulation Research (2023)

Glycogen synthase kinase 3 beta (GSK3β) is a cytosolic serine-threonine kinase first described for inhibiting glycogen synthase. GSK3β structure shows a small sequence that can work as a mitochondrial target sequence, however mitochondrial GSK3β (mtGSK3β) in the heart, and its role have not been investigated. It is known the enzyme can be activated under ischemia-reperfusion (I/R) injury and modulating mitochondrial permeability transition pore (MPTP) opening. In the nervous system, the truncation of GSK3β activates the enzyme, but in the heart, the truncation function remains unknown. We hypothesized that a small subset of GSK3β is truncated and translocated to the mitochondrial matrix, which might modulate MPTP opening . To test our hypothesis, we studied GSK3β expression by Western blot in mitochondrial fractions isolated from differential centrifugation. We found a percentage of GSK3β present in purified mitochondria (Pmito) truncated at the C-terminal side. To evaluate if mtGSK3β is involved in I/R injury, we study its expression in the fractions isolated from hearts subjected to I/R protocol. We found GSK3β is being truncated and its expression was increased in Pmito from I/R-hearts in comparison to normoxia-hearts (controls). To study the role of mtGSK3β in MPTP regulation we measure the sensitivity of the pore under a GSK3β inhibitor, SB216763 (SB21) by fluorescente of Fura-2-FF in a spectrofluorometer. MPTP Ca 2+ -sensitivity was reduced in crude mitochondria fraction (Cm, mitochondria with other organelles) and increased in Pmito under SB21 treatment. This data suggests mtGSK3β is inactive in Pmito and SB21 is inducing MPTP opening by another mechanism. Since GSK3β can be activated and inhibited by phosphorylation at T390 site (pT390) and S9 site (pS9), respectively, we measure it on mtGSK3β. We found pT390 is not present in Pmito likely missing during truncation, while pS9 is in a low amount. Moreover, pS9 increases on Pmito from hearts subjected to I/R protocol. All the data together showed that a small percentage of GSK3β is truncated and translocated within the mitochondrial matrix. However, this mtGSK3β is not involved in the modulation of MPTP opening, since the lack of a C-terminal side causes its inactivation.
Abstract P2084: Adipose Tissues Thermogenesis Provides Cardioprotection Against Diastolic Dysfunction Developed In An Obesity-Induced HFpEF Model
Authors: Jordan Jousma, Jooman Park, Zhenbo Han, Gege Yan, Sarath Babu B Nukala, Youjeong Kwon, Won Hee H Lee, Yuwei Jiang, Sang-Ging Ong
Journal: Circulation Research (2023)

Background: Heart failure with preserved ejection fraction (HFpEF) is a major source of morbidity/ mortality in the United States. A systemic inflammatory state established through underlying comorbidities, such as obesity, is thought to develop cardiac dysfunction in HFpEF. Clinical observations associate adiposity with diastolic dysfunction. Herein we demonstrate that adipose tissue is a direct source of diastolic dysfunction and reveal a cardioprotective role of adipose tissue thermogenesis in obesity related HFpEF. Methods and Results: Mice were treated with a β3-AR agonist, CL-316243 (CL), to induce thermogenesis, followed by HFpEF treatment consisting of HFD and L-NAME. Echocardiography revealed that this protected against HFpEF-induced diastolic dysfunction. Whole heart extracts and AT were then evaluated for the signature of β3-AR signaling. In the heart, no signature of β3-AR signaling was observed. In AT, though, various aspects of β3-AR induced thermogenesis were observed. Histological analysis revelated that CL treatment conferred resistance against obesity-induced whitening of interscapular brown adipose tissue (iBAT). Gene and protein expression changes of thermogenic regulators and lipid metabolism enzymes suggested greater thermogenic activity in CL-treated mice. Accordingly, indirect calorimetry showed enhanced energy expenditure, while regression analysis revealed that AT uniquely contributed to this. Transplantation experiments involving CL-treated donor AT and wild-type donors followed by echocardiographic measurements confirmed that the effects of CL were mediated through AT. This approach was complemented with a genetic model we previously used ( Ucp1 -Cre ERT2 ; Cdkn2a fl/fl ) to promote the expansion of beige AT. Here, beige AT expansion protected against diastolic dysfunction and cardiomyocyte hypertrophy developed during HFpEF. Conclusion: Our study indicates enhanced energy expenditure in AT is cardioprotective in obesity related HFpEF. Furthermore, identifying obese AT as a direct source of diastolic dysfunction highlights the therapeutic potential of targeting AT metabolism as a relevant source of diastolic dysfunction.
Abstract P2037: Bubr1 Is A Critical Regulator Of Cardiac Aging
Authors: Renju Pun, Aradhana Thapa, Sylar Takafuji, Rexton Suzuki, Michael H Kim, Brian North
Journal: Circulation Research (2023)

BubR1 is a serine/threonine protein kinase with a well-established role in regulating the spindle assembly checkpoint during mitosis. Previous studies have shown that BubR1 insufficiency leads to premature aging phenotypes such as kyphosis, cataracts, loss of subcutaneous fat, and a shortened lifespan. Furthermore, BubR1 naturally declines with age a wide range of tissues due to enhanced proteosome-mediated degradation. BubR1 hypomorphic mice expressing approximately 10% of the protein die suddenly in a manner reminiscent of sudden cardiac death. Subsequent studies have further shown that these mice suffer from conduction abnormalities such as a prolonged QTc interval. In humans, the incidence of QTc interval prolongation increases with age, and is associated with sudden cardiac death. Given BubR1 protein levels decline with age, we reasoned that BubR1 is critical for the maintenance of adult cardiac structure and function and its loss with age may drive age-related pathophysiology in the heart. We generated a conditional BubR1 knockout mouse which we crossed to the cardiac-specific cre driver line, Nkx2.5-cre , to assess the consequence of loss of BubR1 specifically in the heart. Electrocardiography analysis of BubR1 heterozygous knockouts also have a prolonged QTc interval in vivo . Structural analysis of the hearts of these mice revealed that they suffer from cardiac hypertrophy as shown by an increase in both heart weight as well as ventricular cardiomyocyte size. Masson’s trichrome staining revealed that BubR1 heterozygous knockout hearts have increased fibrosis both in the ventricular space and the perivascular region. At the molecular level, these mice also show increased levels of p21 and phospho-γH2AX staining, which represent key hallmarks of cellular senescence. Transcriptomic analysis further revealed dysregulation of multiple pathways involved in hypertrophy and senescence. Therefore, reduced expression of BubR1 drives cardiac aging as observed by increases in cardiac hypertrophy, fibrosis, senescence, and DNA damage response. Our results indicate that BubR1 plays a vital role in regulating adult cardiac structure and function, and its loss with age may drive deleterious phenotypes during heart aging.
Abstract P3178: Gja1-20k Is Downstream Of Drp1 And Can Rescue Drp1 Suppression In Mouse Heart
Authors: Jennifer Hunter, Vu D Nguyen, Tingting Hong, Robin M Shaw, Daisuke Shimura
Journal: Circulation Research (2023)

Dynamin-Related Protein 1 (DRP1) is a major mediator of mitochondrial fission and its mutation results with hyper-fused mitochondria and, in mice, a dilated cardiomyopathy. GJA1-20k is the most abundant N-terminus truncated isoform of Connexin 43 (Cx43) formed by internal translation and was originally identified as a trafficking subunit of Cx43. It has been recently identified that GJA1-20k is located on the mitochondrial membrane and plays a role in mediating ischemia preconditioning by promoting a protective mitochondrial fission. Interestingly, GJA1-20k mediated fission occurs even under DRP1 inhibition in vitro. Here, we hypothesize that GJA1-20k is downstream of DRP1 and that exogenous GJA1-20k administration rescues hyper-fusion of mitochondria in DRP1-suppressed mouse hearts. Using an AAV9-mediated DRP1 dominant negative mutant (Drp1-K38A) to suppress DRP1, we confirmed that the Drp1-K38A mouse hearts have an increase in cardiac mitochondrial size (158.9 ± 3.7% of control) and decrease in cardiac function (ejection fraction is 43.1 ± 1.5% versus 64.0 ± 4.1% in control animals), as assayed by electron microscopy and in vivo echocardiography, respectively. However, the administration of exogenous GJA1-20k via AAV9 transduction normalizes mitochondrial size (net 14.1 ± 3.3% decrease from control group) and rescues cardiac function (ejection fraction 61.6 ± 2.7%), suggesting that the progression to the cardiomyopathy is prevented by GJA1-20k administration. In summary, GJA1-20k functions downstream of DRP1 and can rescue the effect DRP1 suppression on mitochondrial size and cardiac function.
Abstract P2118: Intervention With The Adiponectin Mimetic Peptide ALY688 Protects Against Cardiac Dysfunction Induced By Ischemia Reperfusion Injury
Authors: Jialing Tang, Hye Kyoung Sung, Jun Wu, Ren-Ke Li, Angelica Pignalosa, Henry Hsu, Gary Sweeney
Journal: Circulation Research (2023)

Cardiac ischemia reperfusion injury is associated with significant morbidity and mortality for which there remains a great clinical unmet for effective therapeutics. Adiponectin mediates numerous cardioprotective effects and there has been significant interest in developing adiponectin-based therapeutics. The objective of this study was to evaluate the cardioprotective effect of ALY688 on myocardial remodelling at 48 hours post ischemia reperfusion injury, and cardiac function after 28 days. We used a rat model of myocardial ischemia for 45 min followed by reperfusion ± intravenous ALY688 administration during either ischemia or reperfusion followed by daily subcutaneous injection for 28 days. Acute phase (48h) analysis indicated that, compared with vehicle, ALY688 intervention during ischemia or reperfusion reduced cardiac injury indicated by circulating troponin I level, myocardial DNA oxidation and lipid peroxidation and in tissue sections we observed lower TUNEL staining, neutrophil infiltration and macrophage 1 polarization. Further analysis of inflammation indicated an increase of the pro-resolution cytokine IL-10 and Treg content via Foxp3 detection in animals treated with ALY688. Importantly, echocardiography indicated that after 14 and 28 days ALY688-treated animals had significantly improved cardiac function as well as reduced infarct size. This was associated with reduced fibrosis by Masson trichrome, scanning electron microscopy and established markers of fibrosis at the protein and mRNA level. Overall, our data provide strong evidence for the cardioprotective effects of adiponectin mimetic peptide ALY688 as a novel therapeutic strategy in treating ischemia reperfusion injury.
Abstract P1173: Deciphering CITED4-dependent Signaling In The Heart Through Nascent Proteomics And Secretomics
Authors: Vivien Knobloch, Philipp Schlegel, Leandra Lust, Karim Aljakouch, Chiara Hess, Tim C Kuhn, Vassilios J Bezzerides, Sonja Mittag, Mani Roshan, Norbert Frey, Anthony Rosenzweig, Carolin Lerchenmüller
Journal: Circulation Research (2023)

Objective: Neuregulin-1 (Nrg1) promotes cardiomyocyte hypertrophy, survival, and cell cycle activity through ErbB signaling. It is investigated in clinical trials as a cardioprotective agent; however, its therapeutic use might be limited due to its pro-neoplastic potential for non-cardiomyocytes that makes targeted approaches necessary. High-throughput screening of hypertrophic agonists found that Nrg1 induces CITED4 (C4) expression. C4 is also upregulated in both physiological and pathological cardiac growth and necessary to prevent adverse remodeling in vivo. However, how C4 regulates Nrg1-signaling in the heart is yet unknown. Methods: We combined pulsed-SILAC labeling, click-chemistry and mass spectrometry that allows to capture immediate changes in the proteome and secretome after Nrg1 (12h and 24h) stimulation in siRNA-mediated C4-knockdown (C4KD) and control (ctr) NRVM and complemented this with established cell- and molecular biology techniques to validate and investigate cellular function and molecular signaling. Results: We confirmed dose-dependent C4 mRNA upregulation in response to Nrg1 stimulation in NRVM. Nrg1 downstream signaling through AKT was hindered in C4KD. Computational analysis comparing the nascent proteome after Nrg1 stimulation in C4KD and ctr NRVM revealed that C4 significantly regulates proteins responsible for translation, RNA processing and energy derivation. Consistent with previously observed development of cardiac fibrosis in C4 knockout mice in vivo , we found significant upregulation of TGFb2 in C4KD NRVM. We next confirmed the upregulation of TGFb2 and its downstream effectors in C4KD and ctr, while adenoviral overexpression of C4 led to reduced TGFb2 expression. Additionally, we found TGFb2 secretion increased from C4KD NRVM with Nrg1 stimulation in the nascent secretome. Conditioned media from C4KD NRVM led to an increased pro-fibrotic response in cardiac fibroblasts. In conclusion, nascent proteomics and secretomics help to elucidate C4-dependent Nrg1-signaling, which may be an important contribution toward our goal to identify targetable cardioprotective pathways in the heart.
Abstract P1037: Dysfunction Of N-terminal Acetylation Causes Multiple Electrical Abnormalities Leading To Long QT Syndrome And Dilated Cardiomyopathy
Authors: Daisuke Yoshinaga
Journal: Circulation Research (2023)

Introduction: NAA10-related syndrome is characterized by long QT syndrome (LQTS), cardiomyopathy, hypotonia, and neurodevelopmental delay. NAA10 complexes with the regulatory subunit NAA15 to make the post-translationally modifying N-terminal acetyltransferase, NatA. Despite the association of LQTS and NAA10 mutations, the mechanism is unknown. Hypothesis: NAA10 dysfunction affects the function of cardiac ion channels or related proteins causing LQTS, and sarcomere abnormalities causing cardiomyopathy. Methods: Target sequencing of large kindred with multiple family members who had LQTS and sudden death revealed a segregating mutation in NAA10 (c.10C&gt;A; p.R4S). Somatic cell reprogramming was used to create an induced pluripotent stem cell (iPSC) line from a gene-positive male patient with LQTS and dilated cardiomyopathy (pNAA10 R4S ). Genome-editing was used to create the control iPSC line (eNAA10 R4S ). iPSC lines were differentiated into cardiomyocytes (iPSC-CMs) for further analysis. In addition, we performed biochemical assays to investigate the enzymatic activities of the NAA10-R4S mutation. Results: The NAA10-R4S mutation had reduced enzymatic activity, decreased expression levels of NAA10/NAA15 and destabilized the NatA complex. Action potential duration was prolonged in pNAA10 R4S - and eNAA10 R4S -iPSC-CMs as compared to WT iPSC-CMs (498.9 ± 38.8 ms and 514.1 ± 52.9 ms, vs 316.7 ± 48.2 ms; p&lt;0.05). Investigation of the underlying ion channel currents revealed increased late I Na (Late I Na / Peak I Na : pNAA10 R4S : 0.062 ± 0.010 % and eNAA10 R4S : 0.074 ± 0.020 % vs. WT: 0.026 ± 0.005 %; p&lt;0.05) and reduced I Ks (pNAA10 R4S : 0.18 ± 0.05 pA/pF and eNAA10 R4S : 0.26 ± 0.04 pA/pF vs. WT: 0.61 ± 0.15 pA/pF; p&lt;0.05). There were no significant differences in I Kr and I CaL . Diastolic Ca 2+ levels were increased in mutant iPSC-CMs (F340/F380: 0.18 ± 0.02 vs 0.04 ± 0.01; p&lt;0.05) consistent with impaired Ca 2+ handling. Plating iPSC-CMs on micro-contact printed islands revealed alterations in sarcomeric structure. Conclusion: We demonstrate that the NAA10 mutation cause abnormalities in ion channels and sarcomere development. Our data indicated a novel role for N-terminal acetylation in cardiac ion channel regulation leading to cardiovascular disorders.
Abstract P1050: The Activity Of Autophagy Biomarkers In Acute Myocardial Infarction
Authors: Min Gyu Kong, Jon Suh, Yoonhaeng Cho, Hyun Woo Park, Nae Hee Lee
Journal: Circulation Research (2023)

Purpose: We aimed to evaluate the activity of autophagy in patients with AMI. Furthermore, this study analyzed the associations of autophagy biomarkers with the traditional cardiac biomarkers, echocardiographic left ventricular ejection fraction (LVEF) and the defect size of myocardial SPECT. Methods: AMI patients with urgent coronary revascularization and controls who underwent coronary angiography without significant coronary artery stenosis were enrolled prospectively. We obtained the serum of patients from peripheral artery and coronary artery before coronary revascularization. Levels of LC3-II, ATG5, Beclin 1 and M30 were quantified by ELISA in the serum from 71 AMI patients and 46 controls. Results: AMI patients had significant higher concentrations of autophagy biomarkers such as LC3-II (217.0±87.5 vs. 58.1±53.2 ng/ml; 218.6±72.4 vs. 58.7±53.7 ng/ml; p&lt;0.001), ATG5 (183.7±100.1 vs. 35.8±34.2; 169.6±85.3 vs. 38.3±43.1; p&lt;0.001), and Beclin 1 (194.9±86.2 vs. 62.0±53.5; 178.0±67.1 vs. 58.7±50.1; p&lt;0.001) in peripheral artery and coronary artery. All autophagy biomarkers in both arteries had strong positive correlations with traditional cardiac biomarkers including CK-MB, Troponin T, and NT-proBNP. Especially, LC3-II in coronary artery was significantly correlated with the defect size (%) on myocardial SPECT (r s =0.333, p=0.010) in AMI patients. Conclusions: Autophagy biomarkers were significantly higher in AMI patients than in controls. Autophagy biomarkers had significant positive correlations with the traditional cardiac biomarker. LC3-II was significantly correlated with the LV defect size due to myocardial injury in AMI patients.